JPH0357114B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for purifying alkoxysilane, and specifically, a method for removing impurities caused by chlorine contained in alkoxysilane to an extremely trace amount. This invention relates to a method for purifying alkoxysilane that can produce

[Prior Art] In recent years, the use of alkoxysilanes in the electrical and electronic fields has been increasing. There is an urgent need to develop purification methods to obtain silane.

By the way, alkoxysilanes represented by RmSi(OR ¹ ) ₄ -m can be obtained by contacting the corresponding chlorosilane and alcohol in a liquid phase or gas phase. The obtained alkoxysilane has conventionally been purified by neutralizing it with a neutralizing agent and then separating it from non-volatile components such as neutralized salt by distilling the alkoxysilane. However, in this method, no matter which one of dry ammonium, amines, basic compounds containing alkali metals such as sodium, potassium, magnesium, etc. is used as a neutralizing agent, hydrolyzable chlorine such as hydrogen chloride or chlorosilane is used. The disadvantage is that impurities originating from non-hydrolyzable chlorine, such as chlorine atoms bonded to carbon atoms such as chloromethyltrimethoxysilane, cannot be removed, since only impurities originating from chlorine form neutralizing salts. It was hot.

In an attempt to remove impurities caused by this non-hydrolyzable chlorine, for example, the Journal of
Organometallic Chemistry, 265 (1984), 135−
There is a method described in 139, in which an alkoxysilane containing about 400 ppm of non-hydrolyzable chlorine is mixed with the presence of any one of lithium aluminum hydride, tetramethylglinidine, magnesium oxide, dihydrido dibutyltin, and metallic sodium. It is then heat treated and then distilled.

However, this method removes non-hydrolyzable chlorine contained as an impurity in alkoxysilane.
The drawback was that it was not possible to reduce the concentration below 100 ppm except when metallic sodium was used. Furthermore, when metallic sodium is used, it is possible to reduce the non-hydrolyzable chlorine in the alkoxysilane to 100 ppm or less, but it has the disadvantage that it is extremely dangerous to handle and is therefore not suitable for industrial use. .

[Problems to be Solved by the Invention] As described above, it is difficult to remove impurities caused by chlorine in conventional purification methods, but the present invention solves impurities caused by hydrolyzable chlorine in alkoxysilane. Since both impurities and impurities caused by non-hydrolyzable chlorine can be removed relatively easily, we aim to provide alkoxysilanes with extremely low impurities, especially alkoxysilanes with low electrical conductivity that are useful in the electrical and electronic fields. This is the purpose.

[Means for Solving the Problems and Their Effects] That is, the present invention provides a solution containing impurities caused by chlorine and having the general formula RmSi(OR ¹ ) ₄ -m (wherein R is a hydrogen atom or a carbon atom number of 1 to 1). 8
is a substituted or unsubstituted monovalent hydrocarbon group, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 0 to 3. ) When purifying the alkoxysilane represented by (), at least among the entire purification steps are () a step of heat treating the alkoxysilane in the presence of acid clay or a metal halide, () a step of neutralizing with a neutralizing agent, () The object can be achieved by a method for purifying alkoxysilane, which is characterized by including the steps of sequentially performing the steps of removing neutralized salts.

The method for purifying alkoxysilane containing impurities caused by chlorine according to the present invention may be carried out on crude alkoxysilane produced in the alkoxylation step of chlorosilane, or by a conventional purification method.
The process may be performed on an alkoxysilane in which impurities due to hydrolyzable chlorine have been neutralized and removed, but impurities due to non-hydrolyzable chlorine have not been removed. If the crude alkoxysilane contains a large amount of unreacted impurities such as alcohol, it is desirable to remove them by distillation or the like before carrying out the present invention. In addition, the purification method of the present invention sequentially carries out steps (), (), and (); however, after carrying out step (),
This is because a process of neutralization treatment and removal of neutralized salt is always required.

The alkoxysilane used in the present invention has the general formula RmSi(OR ¹ ) ₄ -m (wherein R and R ¹ are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and Examples include alkyl groups such as methyl, ethyl, propyl and octyl groups, alkenyl groups such as vinyl and allyl groups, phenyl groups,
Examples include aryl groups such as tolyl groups and xylyl groups, aralkyl groups such as benzyl groups, and groups in which some or all of the hydrogen atoms of these monovalent hydrocarbon groups are substituted with cyano groups or halogen atoms. . In addition, R is a hydrogen atom, R ¹
Examples include alkoxyalkyl groups. Moreover, m in the formula is an integer of 0 to 3. )
This is shown in .

Specific examples of this alkoxysilane include trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane, methyldimethoxysilane, methyldiethoxysilane, trimethylmethoxysilane, trimethoxyethoxysilane, methyltrimethoxysilane, methyl Triethoxysilane, tri(2-methoxyethoxy)silane, vinylmethyldiethoxysilane,
Examples include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, phenyltrimethoxysilane, diphenylmethoxysilane, phenylmethyldimethoxysilane, and allyltrimethoxysilane.

Although the mechanism by which the acid clay or metal halide used in step (2) of the present invention acts against non-hydrolyzable chlorine is not clear, it has a catalytic action to extract the non-hydrolyzable chlorine. Therefore, it is thought that non-hydrolyzable chlorine is changed into hydrolyzable chlorine by the heat treatment in step ().

As the acid clay used in the step (), naturally produced acid clay may be used as it is, but it is more preferable to use acid-treated so-called activated clay. Specifically, Nippon Kousaku Hakudosha's K
-500, Tonsil of Süd Chemical GmbH in West Germany
FF, Phytrol 20LM from U.S. Phytrol
Examples include, but are not limited to these.

Furthermore, as the metal halide used in step (), metal chlorides are preferred. In particular, metal chlorides from Groups to Groups of the Periodic Table are preferred, but the range is not limited to these. Specifically, iron chloride, copper chloride, nickel chloride, zinc chloride,
Examples include cobalt chloride, manganese chloride, chromium chloride, molybdenum chloride, cerium chloride, and their iodides, bromides, and fluorides.

As for the amount of acid clay or metal halide used, if it is added in an amount of 0.01% by weight or more based on the weight of the alkoxysilane to be heat treated, it is effective against impurities caused by chlorine. In general, increasing the amount of acid clay or metal halide tends to shorten the heat treatment time, but from an economical perspective,
The preferred range used is 0.05 to 2% by weight of the alkoxysilane being treated.

The heat treatment temperature is usually in the range of 50℃ to 200℃, but if the boiling point of the alkoxysilane to be heat-treated is lower than 200℃, the heat treatment is performed at the boiling point of the alkoxysilane under reflux. is desirable.

The reaction time is influenced by the amount of impurities in the alkoxysilane to be heat treated, the amount of acid clay or metal halide added, and the reaction temperature, but is generally in the range of 30 minutes or more and 10 hours or less.

The neutralizing agent used in step () of the present invention is for neutralizing the hydrolyzable chlorine generated in step () and the acidic compounds incidentally generated from acid clay or metal halide. Therefore, conventional neutralizing agents can be used.
Examples of such neutralizing agents include dry ammonia, amines, basic compounds containing alkali metals such as sodium, potassium, calcium, and magnesium, alkylene oxides, orthoesters, and the like.

To give specific examples, as amines, tertiary amines, secondary amines, and primary amines can all be used, including triethylamine, tributylamine, trioctylamine, N,N-dimethyldodecylamine, diethylamine, dibutylamine, Examples include propylamine, butylamine, octylamine, stearylamine, aniline, pyridine, diphenylamine, quinoline, ethanolamine, diethanolamine, triethanolamine, etc.
Examples of the basic compound containing an alkali metal include sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium methylate, magnesium oxide, sodium carbonate, and magnesium carbonate. Furthermore, examples of alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and examples of orthoesters include trimethyl orthoformate and triethyl orthoacetate.

The amount of these neutralizing agents to be used can be freely selected as required, but it is preferably used in an amount of 1% by weight or less, more preferably 0.5% by weight or less of the alkoxysilane.

The method for removing the neutralized salt produced by the neutralization in step () of the present invention is not particularly limited, and may be appropriately selected as necessary. For example, the neutralized salt may be washed out by washing with water, or may be removed by filtration. Alternatively, the alkoxysilane may be separated from the neutralized salt by distillation. Moreover, in order to remove neutralized salts more effectively, these methods can also be combined.

[Example] Next, the present invention will be explained by giving examples and comparative examples. In the examples, all percentages are by weight.
represents.

Example 1 The properties of methyltrimethoxysilane obtained by methoxylating methyltrichlorosilane by a batch method, neutralizing it with sodium methylate, removing the neutralized salt by filtration, and purifying it by distillation are as follows. Ta. Purity by gas chromatography is 99.8
%, as a result of elemental analysis, the total amount of chlorine was 81ppm, 2
The electrical conductivity when made into an aqueous solution with a concentration of 17.0μs/
cm, and the pH was 4.5.

200g of this methyltrimethoxysilane was transferred to a
ml flask, add acid clay (K-500 manufactured by Nippon Kousaku Shirado Co., Ltd.) to methyltrimethoxysilane.
500 ppm was added and heated under reflux for 2 hours. The heating temperature at this time was 100±2°C.
Next, after removing the acid clay by filtration, it was neutralized with 0.5 g of potassium hydroxide, and washed with ion-exchanged water to remove the neutralized salt. The total amount of chlorine contained in methyltrimethoxysilane purified in this way is 6 ppm.
The electrical conductivity when made into a 2% aqueous solution is 1.67μs/cm,
The pH was 5.43.

As a comparative example, the total chlorine amount of methyltrimethoxysilane was treated in the same manner as above without being heat treated with acid clay.
78ppm, the electrical conductivity of a 2% aqueous solution is 16.5μs/cm,
The pH was 4.9.

Example 2 Crude methyltrimethoxysilane obtained by contacting methyltrichlorosilane in a packed column in continuous countercurrent contact with methanol vapor had the following properties: That is, according to gas chromatography, it contains 16.5% methanol. Furthermore, according to silver nitrate titration after neutralization with sodium methylate, it contained 760 ppm of hydrolyzable chlorine. Moreover, the total amount of chlorine was 1000 ppm. The electrical conductivity of the 2% aqueous solution was 194 μs/cm.

100ml of this crude methyltrimethoxysilane 57.8g
After heating in a flask and removing most of the methanol by distillation, 400 ppm of ferrous chloride was added to the crude methyltrimethoxysilane, and the mixture was heated at 91° C. for 1 hour under reflux. Next, after neutralization with sodium methylate, methyltrimethoxysilane was distilled out by simple distillation. No hydrolyzable chlorine was detected in the methyltrimethoxysilane thus obtained, the total amount of chlorine was 12 ppm, and the electrical conductivity of the 2% aqueous solution was 1.6 μs/cm.

As a comparative example, the total chlorine amount of methyltrimethoxysilane was 248 ppm, which was treated in the same manner as in Example 2 except that the step of adding ferrous chloride and heat treatment was omitted, and the electrical conductivity of a 2% aqueous solution was The speed was 45 μs/cm.

Example 3 Instead of the ferrous chloride used in Example 2, zinc chloride was added at 1% to the crude methyltrimethoxysilane.
The mixture was then heated under reflux at 90 to 95°C for 1 hour. After the same operation as in Example 2, the amount of hydrolyzable chlorine in the purified methyltrimethoxysilane was 10 ppm, and the total amount of chlorine was 59 ppm.
The electrical conductivity of the 2% aqueous solution was 2.1 μs/cm.

Example 4 Instead of the ferric chloride used in Example 2, 1% cerium chloride was added to crude methyltrimethoxysilane, and the mixture was heated under reflux at 90 to 95°C for 1.5 hours. Thereafter, methyltrimethoxysilane was obtained in the same manner as in Example 2. The total amount of chlorine in this is
40ppm, and the electrical conductivity of a 2% aqueous solution is
It was 2.2μs/cm.

Example 5 Instead of the ferrous chloride used in Example 2, ferrous bromide was added at a ratio of 1 part to crude methyltrimethoxysilane.
Example 2 was carried out, except that the mixture was heated at 90 to 95° C. for 2 hours under reflux. As a result, the total amount of chlorine was 48 ppm, and the electrical conductivity was
It was 4.5μs/cm.

Example 6 The total amount of chlorine in purified tetraethoxysilane produced by the conventional method by ethoxylating tetrachlorosilane was 64 ppm, and the electrical conductivity was 8.5 μs/cm
It was hot. 200 g of this tetraethoxysilane was placed in a flask, 500 ppm of acid clay (Phytrol 20LM manufactured by Phytrol) was added, and the mixture was heated under reflux for 1 hour. After the subsequent operations were performed according to Example 1, the total amount of chlorine in tetraethoxysilane was 4 ppm, and the electrical conductivity was 1.0 μs/cm.
It was hot.

[Effects of the Invention] The alkoxysilane purification method of the present invention heat-treats alkoxysilane containing impurities caused by chlorine in the presence of acid clay or metal halides, thereby removing impurities caused by hydrolyzable chlorine. Since both impurities caused by non-hydrolyzable chlorine can be removed, it has become possible to easily obtain alkoxysilane with few impurities and low electrical conductivity, which was difficult to achieve with conventional methods. . Therefore, in addition to the conventional uses of alkoxysilanes, it is particularly useful in electrical and electronic fields that require alkoxysilanes with high purity and low electrical conductivity.

Claims (1)

[Claims] 1 Contains impurities due to chlorine, general formula RmSi(OR ¹ ) ₄ -m (wherein R is a hydrogen atom or a carbon atom number of 1 to 8
is a substituted or unsubstituted monovalent hydrocarbon group, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 0 to 3. ) When purifying the alkoxysilane represented by (), at least among the entire purification steps are () a step of heat treating the alkoxysilane in the presence of acid clay or a metal halide, () a step of neutralizing with a neutralizing agent, () 1. A method for purifying alkoxysilane, comprising the steps of sequentially performing steps for removing neutralized salts.